Path monitoring (e.g., path availability validation, path outage, service availability validation, service outage, etc.) and rapid fault isolation are increasingly important features of networking equipment. Rapid detection of communication failures between network nodes can be desirable, for example, to quickly establish alternative paths. Detection can depend on the hardware and media used in networks. For example, Synchronous Optical Network (SONET) uses alarm signals to notify of failures. However, some media (e.g., Ethernet) do not provide such signaling even if faults are detected; other media may not even detect certain faults in the path, for example, failing interfaces or forwarding engine components. Typically, networks use relatively slow “Hello” mechanisms, usually in routing protocols, to detect failures (e.g., when hardware signaling is unavailable). The time to detect failures in such protocols can be far too long for some applications and can result in loss of large amount of data.